1. Bootstrap Confidence Intervals using Percentiles
Section 3.4
Bootstrap Confidence Intervals using Percentiles

2. Review A bootstrap distribution is shown below. Each dot represents
One data value
One bootstrap statistic
n data values
1000 bootstrap statistics

3. Level of Confidence
Which is wider, a 90% confidence interval or a 95% confidence interval?
(a) 90% CI
(b) 95% CI
A 95% CI contains the middle 95%, which is more than the middle 90%

4. Sample Size Remember the effect of sample size?
The larger the sample size the
(a) wider
(b) narrower
the confidence interval.
The larger the sample size the smaller the variability in the bootstrap distribution, which will make the interval narrower. The larger the sample size, the more precise the estimate.